The very Short Treks will feature previously announced fan-favorite characters voiced by cast members from across the Star Trek universe, including icons Jonathan Frakes as Will Riker, Doug Jones as Saru and Armin Shimerman as Quark, and a new line-up of exciting voices, including Ethan Peck as Spock, Gates McFadden as Dr. Beverly Crusher, Celia Rose Gooding as Uhura, Connor Trinneer as Trip Tucker, Bruce Horak as Hemmer, Noël Wells as Tendi and the legendary George Takei as Sulu.
There are a couple of nice surprises on that list.
I expect that the Very Short Treks won't be entirely non-canon. For instance, some episode might introduce an event, place, or technology that is actually canon even if the events of the episode itself are not canon.
Alternatively, they could be loosely canon in the same way as the Lego Star Wars shows/games, with the rough events and plots being canon even if exact details are not.